首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
本文研究了秋冬季节淡水大米草(Spartina densiflora)沼泽中野生豚鼠(Cavia a perea)的丰度、繁殖和微生境利用,以及其对当地植被和棉鼠类(Sigmodontine)啮齿动物的影响。野生豚鼠喜好S.densiflora覆盖度高的生境。繁殖个体(成体)主要利用矮草为主的斑块,幼体则主要利用禾本科植物为主的斑块。结果说明,野生豚鼠微生境的利用受捕食风险和食物种类的影响。在淡水沼泽中,野生豚鼠的丰度、繁殖、体重和微生境利用没有季节性变化,它们对植物的取食和活动跑道的建造对植被结构和同域的啮齿类动物没有负面影响。通过对具有中度季节性变化的淡水生境中的豚鼠种群和具有高度季节变化的草地和路边中的豚鼠种群进行比较,表明野生豚鼠的种群动态以及豚鼠种群对植被和与其共生的啮齿动物群落的影响都受到冬季植被盖度的限制。  相似文献   

2.
    
据预测,人为气候变化将季节性地增加平均温度和降雨。热带雨林物种将如何应对这种气候变化仍不确定。本研究分析了对澳大利亚昆士兰北部丹特里雨林的一种澳大利亚特有棕榈(Normambya normanbyi)进行4年降雨实验的影响,目的是了解模拟降雨减少对物种生理过程和果实物候的影响。我们考察了这种本地丰富的棕榈的果实物候和生理生态学特性,以确定该物种对干旱的生态响应。2015年5月,通过排涝实验,降低了约30%的土壤水分有效性。我们总共监测了8年(2009–2018年)的月度果实活性,包括排涝实验开始之前的4年。在最近几年的研究中,我们测量了干、湿两季幼嫩和成熟叶片的光合速率、气孔导度和碳稳定同位素等生理参数。研究结果表明,所有棕榈树的月度果实活性主要受光周期、平均太阳辐射和平均温度的驱动。然而,暴露于较低土壤水分的植株,其果实活性、光合速率和气孔导度均显著下降。我们还发现这些生理表现受到排涝实验、季节以及两者的相互作用的影响。2018年观察到排涝实验的棕榈的果实活力有所恢复,土壤浅层水分也有所增加(与前几年相比)。我们的研究结果表明,像N. normanbyi 这样的棕榈树对未来的气候变化非常敏感,建议对其进行长期监测,以确定其对种群规模的影响。  相似文献   

3.
Captive bonnet macaques housed at the California Primate Research Center reproduce seasonally. The chances of producing surviving infants were substantially reduced among females who conceived at the peak of the mating season compared with females whose conceptions were more isolated in time. Primiparous females and low ranking females were most consistently affected by the extent of reproductive synchrony. Behavioral data suggest that harassment of conceiving and pregnant females may have contributed to the correlation between the extent of reproductive synchrony and infant mortality as the levels of aggression toward females were highest during the months in which conceptions were most common.  相似文献   

4.
5.
6.
We analyzed birth dates recorded during an 18-year period in a group of Japanese macaques housed in the Rome zoo to assess the influence of environmental, physiological, and social factors on birth seasonality. Birth timing differed significantly among years. Birth timing was affected by reproductive condition of females—ones that had given birth in the previous year delivered significantly later than those that had not—but not by their age or dominance rank. We conducted further analyses separately on females that had or had not given birth in the previous year. In both subgroups of females mean birth date was not influenced either by environmental temperature and rainfall during the previous mating season or by group size. On the contrary, among females that had not given birth in the previous year, socionomic sex ratio—ratio of sexually mature males to sexually mature females—is positively correlated with both mean birth date and date of the first birth, but not with date of the last birth. Contrarily, among females that had given birth in the previous year, there is no significant relationship between these variables. We hypothesize that the effects of socionomic sex ratio on birth timing might depend on competition among males for access to fertile females. When the number of males per female was higher, mutual disruption of consort pairs may have led to a delay in the onset of mating.  相似文献   

7.
全球气候变化对野生动物的影响   总被引:13,自引:0,他引:13       下载免费PDF全文
彭少麟  李勤奋  任海 《生态学报》2002,22(7):1153-1159
人类活动所引起的温室气体增加以及由此造成的全球气候变化和对全球生态环境的影响正越来越引起人们的关注,在全球气候变化对野生动物影响的研究中发现,随着全球气温变暖,野生动物的分布区整体上向北移,物修期提前,动物的繁殖及其种群大小,不同的种类做出不同的响应,有的受益于全球变暖,繁殖增加,成活率高,种群壮大,有的受制于这一变化,种群逐渐缩小甚至面临灭绝的威胁,总的来看,全球气候变暖使更多的野生动物无所适从,因此,加强对气候变化在不同层面上对野生动物影响机制的研究,调整野生动物保护措施,对野生动物及其生境的保护,维持生态系统多样性将显得十分重要。  相似文献   

8.
Plant phenology is concerned with the timing of recurring biological events. Though phenology has traditionally been studied using intensive surveys of a local flora, results from such surveys are difficult to generalize to broader spatial scales. In this study, contrastingly, we assembled a continental-scale dataset of herbarium specimens for the emblematic genus of Neotropical pioneer trees, Cecropia, and applied Fourier spectral and cospectral analyses to investigate the reproductive phenology of 35 species. We detected significant annual, sub-annual and continuous patterns, and discuss the variation in patterns within and among climatic regions. Although previous studies have suggested that pioneer species generally produce flowers continually throughout the year, we found that at least one third of Cecropia species are characterized by clear annual flowering behaviour. We further investigated the relationships between phenology and climate seasonality, showing strong associations between phenology and seasonal variations in precipitation and temperature. We also verified our results against field survey data gathered from the literature. Our findings indicate that herbarium material is a reliable resource for use in the investigation of large-scale patterns in plant phenology, offering a promising complement to local intensive field studies.  相似文献   

9.
    
Species following a fast life history are expected to express fitness costs mainly as increased mortality, while slow‐lived species should suffer fertility costs. Because observational studies have limited power to disentangle intrinsic and extrinsic factors influencing senescence, we manipulated reproductive effort experimentally in the cavy (Cavia aperea) which produces extremely precocial young. We created two experimental groups: One was allowed continuous reproduction (CR) and the other intermittent reproduction (IR) by removing males at regular intervals. We predicted that the CR females should senesce (and die) earlier and produce either fewer and/or smaller, slower growing offspring per litter than those of the IR group. CR females had 16% more litters during three years than IR females. CR females increased mass and body condition more steeply and both remained higher until the experiment ended. Female survival showed no group difference. Reproductive senescence in litter size, litter mass, and reproductive effort (litter mass/maternal mass) began after about 600 days and was slightly stronger in CR than IR females. Litter size, litter mass, and offspring survival declined with maternal age and were influenced by seasonality. IR females decreased reproductive effort less during cold seasons and only at higher age than CR females. Nevertheless, offspring winter mortality was higher in IR females. Our results show small costs of reproduction despite high reproductive effort, suggesting that under ad libitum food conditions costs depend largely on internal regulation of allocation decisions.  相似文献   

10.
    
Reproduction is highly demanding in terms of energy expenditure, and the costs and benefits associated with postponing or investing in a reproductive effort are crucial determinants of an individual's fitness. Understanding the reproductive potential of a species under varying ecological conditions offers important insights into the dynamics of its social system. This study provides the first detailed analysis of the reproductive potential of wild- and captive-born golden-headed lion tamarins (Leontopithecus chrysomelas) under captive conditions, based on studbook data compiled during 1984-2000. Litters produced by wild-born females breeding in captivity are similar in size to litters observed in the wild, but smaller than litters of captive-born females. The more stringent ecological conditions experienced by wild-born females during maturation may result in a lifelong effect on litter size. However, interbirth intervals are shorter for wild-born than captive-born females. The relatively smaller burden of infant care that results from having smaller litters may allow wild-born females to sustain the next pregnancy sooner. Reproduction in the Brazilian captive population is highly seasonal for both wild-born females and females born in captivity in Brazil. Changes in photoperiod over a year provide a proximate explanation for changes in the proportion of conceptions and births per month. Outside Brazil, breeding occurs year-round, and no clear birth peak is apparent. Information from field reports that could be used to relate this finding to ecological factors, such as resource availability, is unavailable.  相似文献   

11.
    
The ability of a pest insect species to enter diapause, a physiological state of dormancy, has significant implications for population dynamics and pest management practises in agricultural landscapes. The false codling moth Thaumatotibia leucotreta is a major pest of deciduous and citrus fruit in southern Africa and a quarantine pest of international concern. Apart from an early field assessment that may have been compromised by taxonomic uncertainty surrounding cryptic developing life stages, no studies have investigated diapause induction within an experimental framework for this species, and none to date have used a suite of physiological traits potentially indicative of the diapause state. Here, we subjected larvae to cooling and shortening day length over a period of 14 days [Diapause Treatment (DT) group] relative to a similar‐aged control (CON) group held at optimal rearing conditions (25°C, 12 : 12 L : D) and tested if physiological traits, including resting metabolic rate, body freezing temperature (=supercooling point, equivalent to the low‐temperature mortality threshold) and body condition (body mass, body lipid and water content) varied in a direction that may be reflective of diapause induction. Mean metabolic rate in DT larvae was 0.044 ml CO2/h (mean mass: 52.7 mg), which was significantly higher than in CON larvae [0.025 ml CO2/h, mean mass: 51.5 mg (P = 0.04)]. Supercooling points were not statistically lower in the CON group than in DT larvae (DT:?15.6 ± 1.5°C; CON: ?16.4 ± 2.8°C; P = 0.33). Measures of body size, body condition and resting water loss rates remained similar between groups. These results support the conclusion of early field observations that T. leucotreta does not undergo diapause that has significant implications for the management of the species.  相似文献   

12.
In captive callitrichid primates, female reproductive function tends to vary with social status. However, little is known about the interplay between these factors in wild groups. We report observations on normative ovarian function in dominant and subordinate female golden lion tamarins (Leontopithecus rosalia) living in wild groups. We monitored ovarian status by measuring, via enzyme immunoassay, concentrations of excreted pregnanediol glucuronide (PdG) and estrone conjugates (E1C) in fecal samples collected noninvasively from individuals in social groups in the Poço das Antas Biological Reserve, Rio de Janeiro State, Brazil. Dominant breeding females demonstrated steroid levels similar to those previously reported for wild cotton-top tamarin females, with statistically significant rises during pregnancy. The duration of elevation of fecal steroids in breeding females was ca. 4 mo, which corresponds with estimates of gestation from captive studies. Low steroid concentrations from December to June suggest a seasonally-related period of infertility in female golden lion tamarins. Dominant and subordinate females demonstrated several differences in endocrine function. In general, younger females living in intact natal family groups showed no evidence of ovarian cyclicity. We noted endocrine profiles consistent with ovulation and subsequent pregnancy for behaviorally subordinate females living in groups with unrelated males or in which a reversal in female dominance status occurred. Results suggest that in addition to changes in female reproductive endocrinology associated with puberty, the regulation of reproduction in females in wild callitrichid groups can be sensitive to status and relatedness to breeding males.  相似文献   

13.
Williams  R. 《Hydrobiologia》1988,165(1):151-159
Selected epifaunal and infaunal species from three sites of differing substrate were examined over a 12 month period. The characteristic species comprising the epifauna at each site were found to be dictated by substrate type whereas the infaunal amphipods and tanaids were relatively similar between sites. No distinct seasonality of abundance was noted for the macroscopic species; however, the infaunal amphipods and tanaids exhibited distinct seasonal cycles of abundance. These temporal changes in population size can be correlated with the seasonal cycle of primary producers. Females, of each of the infaunal species that were monitored, exhibited brood protection throughout the winter period and released juveniles at times that coincided with the period of high primary productivity. All species exhibited properties characteristic of K-strategists; a result of the very stable and predictable nature of the antarctic benthic environment.  相似文献   

14.
    
The fallow deer (Dama dama) is a species of Cervidae commonly kept in captivity, either in commercial farms or in zoos. The reproductive seasonality of this species is well known in the northern hemisphere, where photoperiod is a decisive factor in androgenic activity and, consequently, in the development of secondary sexual characteristics among male adults. The maintenance of this species in tropical regions has been successful, but there are no studies that demonstrate the maintenance of reproductive seasonality under these climatic conditions, which was the objective of the present study. To do so, the present investigation involved 27 fallow deer (D. dama) specimens, of which 14 were adults and 13 prepubescent (<8 months) individuals, all assessed during and outside (December–February) the reproductive season (June–August). The serum concentrations of testosterone, testicular volume, and neck circumference were analyzed among all animals during both seasons. The reproductive season was marked by expressive hormonal concentrations, increasing neck circumference and testicular volume, differing significantly between adults and prepubescent individuals outside the season. Positive correlations were observed among all analyzed variables: mean testicular volume and neck circumference (r = 0.92, p < 0.0001), testicular volume and testosterone concentrations (r = 0.79, p < 0.0001) and between neck circumference and testosterone concentrations (r = 0.67, p < 0.0001). Given the results found, the conclusion is that even under tropical climate conditions the reproductive seasonality of the fallow deer is well defined and may be related to photoperiod.  相似文献   

15.
    
The seasonal dynamics of a dioecious population of Batrachospermum delicatulum (Skuja) Necchi and Entwisle was evaluated biweekly during the growth period of the macroscopic gametophyte, from late autumn (May) to early spring (October) in a third-order stream from the northeast region of Sao Paulo State, southeastern Brazil (20?43'S, 49?13'W). The population fluctuated throughout the study period in terms of percentage cover, frequency and chlorophyll content. Percent cover and frequency showed a clear pattern with the lowest values at the initial and final stages of the growth period and the highest in July-August (winter). Gametophyte growth was associated with high illumination and low temperature, which agrees with most observations on Batrachospermales in stream environments. Relatively wide variations in reproductive characteristics were observed during the growth period, which were not correlated with percentage cover, frequency and chlorophyll content. The phenologic pattern observed in this population was characterized by a synchronic development of female/male plant ratio with the number of spermatangia per plant resulting in: (i) a higher proportion of fertilized (carpo-sporophytic) plants associated with more male plants; (ii) higher fertilization rates during the periods with higher production of spermatangia per plant; and (iii) higher production of spermatangia per plant when the population had more male plants. These characteristics were largely associated with water temperature and ion content. In terms of reproductive success, the population studied can be regarded as highly efficient, considering the relatively low proportion of male to female plants and high fertilization rates. These data are consistent with a hypothesis to explain high fertilization rates in dioecious species in lotic habitats consisting of outcrossing among adjacent plants with intermingled male and female branches within an algal cluster. Efficient reproductive strategies have been reported in dioecious, monoecious and even mixed populations of B. delicatulum and can be interpreted as adaptations to successfully colonize streams with different characteristics.  相似文献   

16.
    
Although maternal photoperiodic and maternal thermal effects on the progeny diapause have been demonstrated in a number of insect species, their interaction has been rarely studied. We investigated this interaction in Trichogramma telengai. In a series of experiments, maternal females were reared at day lengths of 12–18 h and at temperatures of 17, 20, 25 and 30°C. Their progeny developed under day length of 12 h and temperatures of 13, 14 and 15°C. The experiments showed that both short day and low temperature experienced by the maternal generation significantly increased the proportion of diapausing progeny. In particular, the threshold of the maternal photoperiodic response decreased with temperature. Under combinations of photoperiod with daily thermoperiod, the role of the “night” temperature in the induction of diapause in the progeny was much more important than that of the “day” temperature. We conclude that the interaction pattern between the photoperiodic and thermal maternal effects in T. telengai is generally the same as that between the photoperiodic and thermal responses directly influencing diapause induction in other long‐day insects. The threshold temperature of the maternal thermal response of T. telengai was about 25–27°C, while diapause can be induced if larvae develop at temperatures not higher than 15–16°C. This suggests that, at least in the studied Trichogramma species, the maternal thermal effect has no ecological value. In the practice of biocontrol, however, rearing of Trichogramma wasps at high temperature can drastically reduce the proportion of diapausing progeny.  相似文献   

17.
    
Testosterone is strongly associated with the annual development of antlers in cervids, but endocrine research on wild, freely breeding ungulates is often done without repeated capture of known‐aged individuals. As a result, our knowledge on how testosterone fluctuates over the course of a lifetime and variation in lifetime patterns among individuals is limited. We investigated patterns of testosterone in a freely breeding population of white‐tailed deer (Odocoileus virginianus) in Alabama, USA, that breeds in January. Testosterone peaked during the height of the breeding season, despite this period occurring approximately 2 months later than in most temperate‐region white‐tailed deer populations. Age‐related differences in testosterone were only prevalent during the breeding season, with bucks ≥3.5 years old having greater testosterone (853 ng/dl ± 96 SE; p = 0.012) than bucks 1.5–2.5 years old (364 ng/dl ± 100 SE). Additionally, an individual''s testosterone level as a yearling was not positively associated with their lifetime maximum testosterone level (p = 0.583), and an individual''s mean testosterone level was positively associated with lifetime testosterone variation (p < 0.001). To our knowledge, our study is one of the first to assess how testosterone early in life might relate to individual testosterone later in life. We believe these data provide insight into lifetime hormonal patterns in cervids, and that these patterns may indicate intraspecific variation of lifetime reproductive strategies.  相似文献   

18.
    
Understanding the spatio‐temporal distribution of ungulates is important for effective wildlife management, particularly for economically and ecologically important species such as wild boar (Sus scrofa). Wild boars are generally considered to exhibit substantial behavioral flexibility, but it is unclear how their behavior varies across different conservation management regimes and levels of human pressure. To analyze if and how wild boars adjust their space use or their temporal niche, we surveyed wild boars across the core and buffer zones (collectively referred to as the conservation zone) and the transition zone of a biosphere reserve. These zones represent low and high levels of human pressure, respectively. Specifically, we employed a network of 53 camera traps distributed in the Schaalsee UNESCO Biosphere Reserve over a 14‐month period (19,062 trap nights) and estimated circadian activity patterns, diel activity levels, and occupancy of wild boars in both zones. To account for differences in environmental conditions and day length, we estimated these parameters separately for seven 2‐month periods. Our results showed that the wild boars were primarily nocturnal, with diurnal activity occurring dominantly during the summer months. The diel activity patterns in the two zones were very similar overall, although the wild boars were slightly less active in the transition zone than in the conservation zone. Diel activity levels also varied seasonally, ranging from 7.5 to 11.0 h day−1, and scaled positively with the length of the night (R 2 = 0.66–0.67). Seasonal occupancy estimates were exceptionally high (point estimates ranged from 0.65 to 0.99) and similar across zones, suggesting that the wild boars used most of the biosphere reserve. Overall, this result suggests that different conservation management regimes (in this case, the zoning of a biosphere reserve) have little impact on wild boar behavior. This finding is relevant for wildlife management in protected areas where possibly high wild boar densities could interfere with conservation goals within these areas and those of agricultural land use in their vicinity.  相似文献   

19.
20.
Demonstrated that in rodents the duration of ontogenetic development (from conception to the age of eye openin) is allometrically related to the maternal body weight. The differences between actual developmental time and the expected time (counted for animals of that systematic position and that body weight) can be used as a tool to test phylogenetic relationships. As far as the relationships between sister-taxa are concerned, the results of the present analysis corroborate the conclusions of modern classifications. A long developmental time (which means by implication also a long pregnancy and precocity) is couled with hystricognathy and hystricomorhy. These traits must be considered plesiomorphic and their occurrence suggests conservatism of articular taxa. Parallell (coupled) with adopting sciurognathy and, particularly, protrogomorpiy, sciuromorphy, and eventually, myomorphy, rodents were able to shorten their developmental times. In this way they could increase the reproductive rate and made their reproduction more efficient. Consequently the respective taxa radiated more rapidly and successfully.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号